I have some new budget coming up to buy an Equallogic PS6110xv. This unit has 24x600G disks and I'm looking at different ways of setting it up.
The two primary uses will be VMs and MySQL.
MySQL: currently uses about 2T on an older SAN. Expected 3y growth would be an additional 2T. Seems like I should create a 4T partition and be done with it.
VMs: Im consolidating about a dozen retired machines into VMs using two hosts. This is where I'm not fully clear on how much space to allocate and how. Do I create one block with all the expected space or just create space for the basics and then mount additional space from the SAN on an as-needed basis? IE create a volume with 50g x 12 for the OS and then another with 5-6T as a 'pool'? I could mount 'thin' volumes on this as needed.
Last: If I'm using RAID-6 is there any advantage to making the whole device into one raid group? Seems like having that many disks to read for a rebuild is asking for trouble. On the other hand, having multiple smaller groups implies a less efficient use of the media.
Just wondering what the conventional wisdom is.
EDIT: (found this post in a VM group):
No, you can't separate the disks in one array into multiple storage groups or raid levels. Here's a quick cheat sheet on EqualLogic architecture/terminology:
Group - a collection of physical arrays that can be accessed as one resource. They are all managed at the same IP and share the same iSCSI target IP's.
Group member - an entire physical array. The entire (usually 16 spindle) array is essentially one big virtual disk. For RAID-10, by default you have two hot spares which means you have a 14-spindle RAID-10 array. On our PS6000XV with 15K 450GB SAS drives we got about 2.72 TB of usable space with RAID-10.
Storage Pool - a way to logically divide members and volumes within a group. However, both group members and volumes can only be part of one storage pool at a time, meaning you can't take a PS6000XV and dedicate 7 spindles to one storage pool and 7 spindles to the other.
The architecture does seem a bit inflexible on the surface, and it is - at least compared to traditional arrays where you can make as many RAID groups as you want within a single enclosure. Keep in mind that EqualLogic is really good for two things - ease of setup and scaling out.
Ease of setup - With most traditional iSCSI SANs, you have a main enclosure which houses some disks and the controllers. If you need more capacity, you add another enclosure, which usually means bringing the SAN down, adding your enclosure, reconfiguring the array controllers, and finally bringing the array back up. With EQL you just plug it in, enter the groups network information and authentication credentials, and it comes online as a member of your group with no downtime.
Scale out - Again, with traditional iSCSI SANs when you add an enclosure you are essentially doubling (or tripling) the number of spindles that your controllers are responsible for. With EQL, as you add capacity you are also adding dedicated controllers. The marketing people will tell you that this leads to more linear scaling of throughput and latency as you add capacity.
So this implies that I will have one 24 member RAID-6 group. Or 23 with a hot spare...